Struggling to build a circuit to test a 30ua Moving Coil Meter properly
Any Pointers

Many Thanks
Luke

 

A power supply and a resistor. Measure the voltage across the resistor, calculate the current and compare with the meter reading.

 

Welcome to AAC!

30uA is the current for full scale deflection. If you don't have a current source that low, you could install a shunt across the meter so it will take a larger current for full scale deflection.

 

you could install a shunt across the meter so it will take a larger current for full scale deflection.

To get an accurate shunt value you need to know the meter coil resistance.

 

Thanks for the replies
I was thinking of testing the movement with a resistor in series from a 1.5v battery but can't get the math to add up properly.
Meter Resistance is 3250ohms. Its quite a rare movement so don't want to kill it

 

I was thinking of testing the movement with a resistor in series from a 1.5v battery but can't get the math to add up properly.
Meter Resistance is 3250ohms. Its quite a rare movement so don't want to kill it

Go for half scale deflection or less to start:
\(R=\frac{V}{I}=\frac{1.5V}{15uA}=100k\Omega\)

Using a 100k resistor in series would give you slightly less than half scale deflection.
\(I=\frac{V}{R}=\frac{1.5V}{103,250\Omega}=14.5uA\)

 

It would be easy, using an analogue multimeter. In the resistance measuring ranges the multiplier and the test current would be marked. With the required range selected, and with the prods on the terminals of the meter under test (negative prod on positive terminal and vice versa), it should read the test current and the multimeter its coil resistance.